Trucks have long been used to haul material to a location for unloading. To unload the material from the truck bed, the operator might have to physically remove the material by hand, or perhaps with the aid of a shovel. Dump trucks were developed to allow the front of the truck bed to be elevated, allowing gravity to pour the material from the truck bed. While eliminating the physical labor, dump trucks do not provide much control over the amount of material being unloaded. Additionally, the action of pivoting the trailer bed produces significant stress on the underlying vehicle frame. These stresses necessitate the use of heavier frames.
A solution to the problems presented by standard dump truck design is presented in U.S. Pat. No. 4,518,303 to Moser entitled "Movable Floor Self-Unloading Trailer" which issued on May 21, 1985. Moser '303 discloses a self-unloading trailer having a frame with a rotatable sprocket shafts supported at each end and engaged with an endless conveyor type floor. The floor is comprised of a series of side-by-side floor plates which are interconnected by hinge pins and are provided with a plurality of laterally spaced bearing shoes which slide in elongated longitudinally extending channel shaped bearing rails. The movable floor includes a drive sprocket assembly characterized by a series of sprocket segments which are configured to engage the floor plates along the bearing hinge portions. The movable floor is particularly adapted for use in conjunction with a modified general cargo type truck trailer.
An alternate design is disclosed in Moser '089 issued on Apr. 8, 1975 and entitled "Conveyor Equipment, Especially Cargo Loading and Unloading Equipment for a Vehicle." The conveyor includes a slatted floor carried on lugs that are in turn mounted on a closed loop cable. The cable is trained over and driven by notched sheaves at each end of the conveyor frame. The lugs evenly spaced and the slats are attached to the lugs. In one embodiment, the ends of the slats are bent upwardly to provide a conveyer surface which is generally trough shaped.
A need exists for an improved movable floor mechanism. An improved movable floor mechanism should provide a practically seamless surface adjacent to the loaded material. Any open seam is likely to catch large particles such as pebbles and stones which could jam the mechanism. Any exposed seam should be self-cleaning when the floor goes from a curved to a flat configuration. The improved movable floor mechanism should be self interengageable, thereby not requiring the placement of any hinge pins to couple adjacent floor elements. The improved floor should also freely slide over its frame, not relying upon the alignment of bearings with a bearing slide rail.